Catheters are commonly used in the diagnosis and treatment of various medical conditions and advancements in catheter designs and materials have made them particularly well-suited for intravascular procedures and intravascular therapies. A conventional catheter includes a small, elongated tube made of flexible, biocompatible materials that enable the catheter to be easily maneuvered through body passages and vascular structures. During an angiographic procedure, the distal end of the catheter is typically inserted into the body via small incisions in the groin area or upper arm and guided through anatomical passages and/or blood vessels to a target site using guide wires and associated imaging techniques. The proximal end is then connected to the device for performing the desired procedure. One such device is an angiographic injector such as the injector disclosed in U.S. patent application Ser. No. 08/957,228 and/or the injector disclosed in U.S. Pat. No. 5,800,397, both of which are commonly assigned to the owner of the present application and both of which are hereby incorporated by reference.
An example of a procedure using a catheter is angiography. Angiography is a procedure used to specifically image, diagnose and treat abnormalities in the heart or vascular structures. During angiography, a physician inserts a catheter and injects contrast material through the catheter into a vein or artery of a patient. The area of the patient's body injected with the contrast material is imaged using x-ray energy or magnetic fields (as used in magnetic resonance imaging) and the resulting image is recorded and/or displayed on a monitor. The images can be used for many purposes, including diagnostic activities as well as interventional procedures such as angioplasty, wherein a balloon is inserted into a vascular system and inflated to open a stenosis.
During the injection procedure, fluid typically flows out of the open distal end of the catheter tip. However, the fluid dynamics associated with some catheter designs often cause the catheter to be pushed back or to recoil as a result of the velocity of the fluid as it exits the distal tip. In effect, the recoil force of the catheter is directly proportional to the fluid velocity at the tip.
Such undesirable recoil movement is particularly acute when using a catheter of small size, e.g. less than about 4 French, since these catheters experience particularly high fluid exit velocities due to the flow requirements in a typical angiographic procedure. However, even larger catheters may be prone to higher recoil if fluid flow out of the tip is of sufficient velocity. Overall, however, smaller angiographic catheters are more prone to severe whipping and recoil at the outset of an injection than catheters of a larger size. This, in part, is due to the structural characteristics of the catheters. In particular, as catheter shaft diameter decreases, the bending force is reduced by the diameter to the third power. Thus, a reduction in shaft diameter from 6 to 4 French gives a four fold reduction in bending force given the same load and distance at which the load is applied.
Catheter designs incorporating valves or openings located along the distal portion of the catheter wall have been considered in an attempt to better facilitate control of the fluid flow. An example of such a device may be found in U.S. Pat. No. 5,250,034, which discloses a pressure responsive valve catheter. The catheter is formed of a relatively non-compliant material, such as nylon, to prevent the sidewalls of the catheter from expanding under the high internal fluid pressures. Slits formed in the catheter wall act as pressure responsive valves to permit fluid to exit the internal lumen of the catheter while preventing material from entering the catheter lumen via the slits. The catheter also includes a distal end hole which may be sealed with an occluding ball located on a guide wire, thereby causing all the fluid to flow from the slits. Alternatively, when the occluding ball is not seated in the end hole, both the fluid and guide-wire may exit from the end hole.
Another example may be found in U.S. Pat. No. 5,807,349, which discloses a catheter having a valve mechanism to permit the infusion or aspiration of fluids between the catheter and the vessel in which the catheter is positioned. The valve is located at the distal end of the catheter and, preferably, is in a plane which is oriented at an angle to the longitudinal axis of the catheter.
The above-described catheters used during angiographic procedures (and other similar devices not specifically described) offer many advantages to control fluid flow. However, it has been discovered that these catheter designs do not adequately address problems with catheter recoil within the vessel or body cavity. Further, these and other state of the art catheter valve mechanisms may still suffer from erratic opening and closing of the valves which can trigger catheter recoil. Furthermore, none of these designs nor any other designs known to the inventors appear to address the particularly acute problem of recoil with small (e.g. less than about 4 French) catheters used in angiography procedures.
In this connection, it is also important to note that there is a continuing need and desire in the medical field to reduce trauma to patients that are undergoing invasive therapies. In the context of catheter placement, this desire has led to a consideration of how to reduce patient trauma during the placement and removal of the interventional catheter.
In current techniques, the catheters that are used require a sizable incision in the patient such that there is considerable pain encountered by the patient and considerable attention to wound control is demanded of the clinician. Indeed, the wound created for such procedures requires the clinician to apply a sizable bandage or other wound containment device (e.g., a product known as Perclose from Percutaneous Vascular Surgery) in order to ensure proper treatment and closure of the wound. Furthermore, such a wound requires significant time in order for proper healing to occur.
As a result, there is an increasing desire to use smaller sized catheters in such interventional therapies so as to make the intervention as minimally invasive as possible. Such small catheters require a significantly smaller incision and thus trauma is reduced and quicker healing is obtained. However, as stated previously, such smaller catheters typically are accompanied with drawbacks such as undesirable flow characteristics (e.g. recoil).
In view of the above, although presently available catheters seem well accepted by the medical community and generally function as required, it is desirable to have a catheter with more controlled fluid flow characteristics and less invasive attributes. In particular, it is desirable to have a small diameter catheter that allows for the management of fluid forces to stabilize the distal tip over a wide range of injection parameters. It is also desirable that there be substantially low or no recoil of the catheter tip in a small diameter catheter during high volume injections, such as those associated with coronary or ventricular angiography. In addition, it is desirable to have a “universal” catheter that may be used for a variety of surgical procedures and that reduces trauma inflicted on the patient. The concept of a “universal” catheter, as applied to the present invention, is similar to a muzzle brake device that attaches to the outside barrel of any firearm and functions to reduce recoil of the firearm while maintaining discharge accuracy. Therefore, as with the muzzle brake device, it is desirable that the present invention is adaptable to a variety of catheter designs and reduces catheter movement during various medical procedures.